Comparison of different methods for determining the moisture diffusivity of porous building materials

Peng Ren,Chi Feng,Hans Janssen,R Černý,J Kočí,V Kočí

doi:10.1051/matecconf/201928202023

Abstract

This paper compares the X-ray method, the ruler method and the multi-step method to non-destructively determine the moisture diffusivity of calcium silicate and ceramic brick. Results show that the ruler method and multi-step method produce acceptable diffusivities and λ-profiles compared with the common X-ray method, meaning that both methods can determine moisture diffusivity reliably to some extent without the expensive X-ray setup and complicated data processing.

Highlights

The moisture diffusivity, as an important hygric property, is relevant to moisture transfer in building materials, and as such influences construction durability, energy consumption of buildings, and even human comfort and health [1, 2]
Results show that the ruler method and multi-step method produce acceptable diffusivities and λprofiles compared with the common X-ray method, meaning that both methods can determine moisture diffusivity reliably to some extent without the expensive X-ray setup and complicated data processing
For ceramic brick (Fig. 2 right), the λ-profile from the ruler method nearly overlaps with the X-ray result for λ 0 to 0.0027 m/s0.5, but it drops sharply at higher λ, causing a deviation on the values of capillary absorption coefficient

Summary

Introduction

The moisture diffusivity, as an important hygric property, is relevant to moisture transfer in building materials, and as such influences construction durability, energy consumption of buildings, and even human comfort and health [1, 2]. Most of the well-established and non-destructive methods rely on expensive laboratory equipment, such as X-ray projection methods, computerized tomography techniques and nuclear magnetic resonance approaches [3, 4] These methods are obviously able to determine the moisture diffusivity reliably, the high equipment price causes that only a few laboratories are capable to conduct moisture diffusivity measurements, which is not conducive to in-depth research developments, and even affects the development process in the entire moisture transfer field. In 2018, Bianchi Janetti [6] proposed to approximate the moisture https://doi.org/10.10 51/matecconf /201928202023 diffusivity as a multi-step function of moisture content to estimate the moisture content profile of building material In this method, a series of capillary uptake tests with specimens at different initial moisture contents are performed to characterize this multi-step diffusivity. The accuracy of this method was only verified by simulation

Methods

Results

Conclusion